1. Field of the Invention
The present invention relates to an image processing unit for converting image signals to recording signals. More specifically, the present invention is applicable to an apparatus for preventing a line break which is caused when an image is reproduced by halftone dot signals.
2. Description of the Background Art
In order to reproduce an image of a read original, variable densities of the image are generally expressed in sizes of halftone dots, i.e., area rates. In this case, the read image is compared with a screen pattern having a prescribed angle which is repeated in a prescribed cycle, to determine the area rates of the respective halftone dots. Thus, the halftone dots themselves have the said prescribed angle as the angle of arrangement.
However, the image may not be continuously reproduced due to relation between the positions of pixels forming the read original and the halftone dot area rates, since the halftone dots themselves have the aforementioned angle of arrangement. Namely, this leads to the so-called line break phenomenon. Particularly when the image contains thin lines having narrow widths, a remarkable line break phenomenon is caused in relation to such thin lines.
Such a line break phenomenon, which is caused not only by the positions of pixels forming the read original and the halftone dots but by the halftone area rates and sampling rates of image signals, has been generally regarded as an unavoidable phenomenon in principle for the method of expressing the variable densities through the sizes of the halftone dots for reproducing the image. If such a line break phenomenon takes place, therefore, a skilled operator draws an appropriate line on a film, to correct the portion causing the line break.